Data compression and expansion of an audio signal

ABSTRACT

A data compression apparatus is disclosed for data compressing an audio signal. The data compression apparatus comprises an input terminal ( 1 ) for receiving the audio signal, a 1-bit A/D converter ( 4 ) for A/D converting the audio signal so as to obtain a bitstream signal, a lossless coder ( 10 ) for carrying out a lossless data compression step on the bitstream signal so as to obtain a data compressed bitstream signal, and an output terminal ( 14 ) for supplying the data compressed bitstream signal. Further, a recording apparatus and a transmitter apparatus comprising the data compression apparatus are disclosed. In addition, a data expansion apparatus for data expanding the data compressed bitstream signal supplied by the data compression apparatus is disclosed, as well as a reproducing apparatus and a receiver apparatus comprising the data expansion apparatus.

This is a continuation of application Ser. No. 08/937,435, filed Sep.25, 1997, now U.S. Pat. No. 6,269,338 issued 31 Jul. 2001.

FIELD OF THE INVENTION

The invention relates to the field of data compression and most closelyrelates to real time compression of a digitally sampled audio datastream.

BACKGROUND OF THE INVENTION

The invention relates to a data compression apparatus for datacompressing an audio signal, to a data including compression method, atransmitter including the data compression apparatus, a recordingapparatus including the data compression apparatus, a record carrierhaving the data compressed audio signal recorded on it in a track of therecord carrier, to a data expansion apparatus for data expanding a datacompressed audio signal, to a data expansion method a receiver includingthe data expansion apparatus and to a reproducing apparatus includingthe data expansion apparatus.

Data compression on an audio signal is well known in the art. Referenceis made in this respect to EP-A 402,973, document D1 herein. Thedocument describes a subband coder, in which an audio signal is A/Dconverted with a specific sampling frequency, such as 44.1 kHz, and theresulting samples in the form of eg. 24 bits wide words of the audiosignal, are supplied to a subband splitter filter. The subband splitterfilter splits the wideband digital audio signal into a plurality ofrelatively narrow band subband signals. Using a psycho acoustic model, amasked threshold is derived and blocks of samples of the subband signalsare subsequently quantised with a specific number of bits per sample foreach block of the subband signals, in response to the masked threshold,resulting in a significant data compression of the audio signal to betransmitted. The data compression carried out is based on ‘throwingaway’ those components in the audio signal that are inaudible and isthus a lossy compression method. The data compression described indocument D1 is a rather intelligent data compression method and requiresa substantial number of gates or instructions, when embodied either inhardware or software, so that it is expensive. Moreover, the subsequentexpansion apparatus also requires a substantial number of gates orinstructions, when implemented in hardware or software-respectively.

Those skilled in the art are hereby referred to the following listeddocuments:

(D2) “A digital decimating filter for analog-to-digital conversion ofhi-fi audio signals”, by J. J. van der Kam in Philips Tech. Rev. 42, no.6/7, April 1986, pp. 230-8

(D3) “A higher order topology for interpolative modulators foroversampling A/D converters”, by Kirk C. H. Chao et al in IEEE Trans. onCircuits and Systems, Vol. 37, no. 3, March 1990, pp. 309-18

(D4) “A method for the construction of minimum-redundancy codes”, by D.A. Huffman in Proc. of the IRE, Vol. 40(10), September 1952.

(D5) “An introduction to arithmetic coding” by G. G. Langdon, IBM J.Res. Develop., Vol. 28(2), March 1984.

(D6) “A universal algorithm for sequential data compression” by J. Zivet al, IEEE Trans. on Inform. Theory, Vol. IT-23, 1977.

The above citations are hereby incorporated in whole by reference.

SUMMARY OF THE INVENTION

The invention aims at providing a data compression apparatus for datacompressing an audio signal such that it is more simple and that thecorresponding expander apparatus can also be more simple and lessexpensive.

The data compression apparatus in accordance with the invention includes

input apparatus for receiving the audio signal,

conversion apparatus for carrying out a conversion on the audio signalso as to obtain a 1-bit bitstream signal, the conversion apparatusincluding sigma-delta modulator apparatus,

lossless coding apparatus for carrying out a substantially lossless datacompression step on the bitstream signal so as to obtain a datacompressed bitstream signal, and

output apparatus for supplying the data compressed bitstream signal.More specifically, when the audio signal is an analog audio signal, theconversion apparatus is in the form of A/D conversion apparatus forcarrying out a 1-bit A/D conversion on the analog audio signal so as toobtain the bitstream signal.

The invention is based on the following recognition. The audio signalcan be applied in analog form or in digital form. When A/D converting,in accordance with the invention, an analog audio signal with a 1-bitA/D converter (also named: bitstream converter or sigma-deltamodulator), the audio signal to be A/D converted is sampled with afrequency which is generally a multiplicity of the frequency of 44.1 kHzor 48 kHz. The output signal of the 1-bit A/D converter is a binarysignal, named bitstream signal. When the audio signal is supplied indigital form, sampled at eg. 44.1 kHz, the samples being expressed ineg. 16 bits per sample, this digital audio signal is oversampled with afrequency which is again a multiplicity of this sampling frequency of44.1 kHz (or 48 kHz), which results in the 1-bit bitstream signal.

Converting an audio signal into a 1-bit bitstream signal has a number ofadvantages. Bitstream conversion is a high quality encoding method, withthe possibility of a high quality decoding or a low quality decodingwith the further advantage of a simpler decoding circuit. Reference ismade in this respect to the publications ‘A digital decimating filterfor analog-to-digital conversion of hi-fi audio signals’, by J. J. vander Kam, document D2, and ‘A higher order topology for interpolativemodulators for oversampling A/D converters’, by Kirk C. H. Chao et al,document D3 in the list of related documents.

1-bit D/A converters are used in CD players, as an example, to reconvertthe bitstream audio signal into an analog audio signal. The audio signalrecorded on a CD disk is however not a data compressed 1-bit bitstreamsignal.

It is well known in the art that the resulting bitstream signal of the1-bit A/D converter is, roughly, a random signal which has a‘noisy-like’ frequency spectrum. Such types of signals are hard to datacompress.

Surprisingly, however, it was established that using a lossless coder,such as a variable length coder in the form of a Huffman coder or anarithmetic coder, a significant data reduction could be obtained, inspite of the noisy character of the bitstream signal from the 1-bit A/Dconverter.

BRIEF DESCRIPTION OF THE DRAWINGS

Those skilled in the art will understand the invention and additionalobjects and advantages of the invention by studying the description ofpreferred embodiments below with reference to the following drawingswhich illustrate the features of the appended claims:

FIG. 1 shows an embodiment of the data compression apparatus.

FIG. 2a shows the frequency spectrum of the output signal of the 1-bitA/D converter 4 in FIG. 1 and FIG. 2b shows the frequency spectrum ofthe same output signal in a smaller frequency range.

FIG. 3 shows the data compression apparatus incorporated in a recordingapparatus for recording the data compressed bitstream signal on a recordcarrier.

FIG. 4 shows the data compression apparatus incorporated in atransmission apparatus for transmitting the data compressed bitstreamsignal via a transmission medium.

FIG. 5 shows an embodiment of the data expansion apparatus.

FIG. 6 shows the data expansion apparatus incorporated in a reproducingapparatus for reproducing the data compressed bitstream signal from arecord carrier.

FIG. 7 shows the data expansion apparatus incorporated in a receivingapparatus for receiving the data compressed bitstream signal from atransmission medium.

FIG. 8 shows a further embodiment of the recording apparatus furtherprovided with an error correction encoder and a channel encoder.

FIG. 9 shows a further embodiment of the reproducing apparatus furtherprovided with a channel decoder and an error correction unit.

FIG. 10 shows an embodiment of the data compression apparatus in whichthe lossless coder is in the form of an arithmetic coder.

FIG. 11 shows an embodiment of the data expansion apparatus in which thelossless decoder is in the form of an arithmetic decoder.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows an embodiment of the data compression apparatus, includingan input terminal 1 for receiving the audio signal. In the presentexample, the audio signal is an analog audio signal. The input terminal1 is coupled to an input 2 of a 1-bit A/D converter 4, also called:sigma-delta modulator. An output 6 of the 1-bit A/D converter 4 iscoupled to an input 8 of a data compression unit 10. An output 12 of thedata compression unit 10 is coupled to an output terminal 14.

The 1-bit A/D converter 4 is adapted to carry out a 1-bit A/D conversionon the audio signal so as to obtain a bitstream signal which is suppliedto the output 6. To that purpose, the A/D converter 4 receives asampling frequency equal to N*−f_(s) via an input 16. Wherein f_(s) is afrequency equal to eg. 32 kHz, 44.1 kHz or 48 kHz and N is a largenumber, such as 64. The audio signal is sampled in the A/D converter 4with a sampling frequency of eg. 2.8224 MHz (64*44.1 kHz). The bitstreamsignal appearing at the output 6 of the A/D converter thus has a bitrateof 2.8224 MHz.

The data compression unit 10 is in the form of a lossless coder.Lossless coders have the advantage that they can data compress the audiosignal in such a way that, after data expansion by a lossless decoder,the original audio signal can be reconstructed in a substantiallylossless way. Thus, there is substantially no loss of information aftercompression-expansion. Lossless coders can be in the form of a variablelength coder. Variable length coders are well known in the art. Examplesof such variable length coders are Huffman coders, arithmetic coders andLempel-Ziv coders. Reference is made in this respect to the publications‘A method for the construction of minimum-redundancy codes’ by D. A.Huffman, document D4, ‘An introduction to arithmetic coding’ by G. G.Langdon, document D5, and ‘A universal algorithm for sequential datacompression’ by J. Ziv et al, document D6.

The data compression unit 10 carries out a substantially lossless datacompression step on the bitstream signal so as to obtain a datacompressed bitstream signal at its output 12, which is supplied to theoutput terminal 14.

FIG. 2a shows a frequency spectrum of the bitstream signal present atthe output 6 of the A/D converter 4, for an input signal in the form ofa 5 kHz sinusoid, sampled with a sampling frequency of 2.8224 MHz. Thespectrum thus shows frequencies between 0 Hz and 1.4 MHz. FIG. 2b showspart of the spectrum shown in FIG. 2a, namely that part between 0 Hz and100 kHz, so as to more clearly show the 5 kHz sinusoid contained in thebitstream signal. Clearly visible is the noise-like character of thebitstream signal, especially in the higher frequency region, which seemsto imply that carrying out data compression on the signal will notresult in a substantial amount of data reduction.

Contrary to this, investigations have made clear that a significant datareduction can be obtained. In the following table, the results of thedata compression realized by three lossless coders are given for threedifferent music fragments:

δ fragment Huffman (8 b) Hufmann (16 b) Lempel-Ziv bossanova 1.31 1.451.73 jazz 1.35 1.50 1.77 classical music 1.38 1.59 1.86

where δ is the compression ratio, defined as the ratio of the bitrate ofthe input signal of the coder to the bitrate of the output signal of thecoder.

FIG. 3 shows an embodiment of a recording apparatus including the datacompression apparatus shown in FIG. 1. The recording apparatus furtherincludes a write unit 30 for writing the data compressed bitstreamsignal in a track on the record carrier 32. In the present example, therecord carrier 32 is a magnetic record carrier, so that the write unit30 includes at least one magnetic head 34 for writing the datacompressed bitstream signal in the record carrier 32. The record carriermay however be an optical record carrier, such as a CD disk or a DVDdisk.

FIG. 4 shows an embodiment of a transmitter for transmitting an audiosignal via a transmission medium TRM, including the data compressionapparatus as shown in FIG. 1. The transmitter further includes atransmission unit 40 for applying the data compressed bitstream signalto the transmission medium TRM. The transmission unit 40 could includean antenna 42.

Transmission via a transmission medium, such as a radio frequency linkor a record carrier, generally requires an error correction encoding anda channel encoding carried out on the data compressed bitstream signalto be transmitted. FIG. 8 shows such signal processing steps carried outon the data compressed bitstream signal for the recording arrangement ofFIG. 3. The recording arrangement of FIG. 8 therefore includes an errorcorrection encoder 80, well known in the art, and a channel encoder 82,also well known in the art.

FIG. 5 shows an embodiment of the data expansion apparatus. Theapparatus has an input terminal 50 for receiving the data compressedaudio signal which is in the form of the data compressed bitstreamsignal, as supplied by the data compression apparatus of FIG. 1. Theinput terminal 50 is coupled to an input 52 of a data expansion unit 54,which has an output 56 which is coupled to an input 58 of a 1-bit D/Aconverter 60. An output 62 of the converter 60 is coupled to an outputterminal 64.

The data expansion unit 54 is a lossless decoder, such as a variablelength decoder in the form of eg. a Huffman decoder or an arithmeticdecoder. It will be clear that the decoder in the data expansionapparatus of FIG. 5 should be the inverse of the encoder used in thedata compression apparatus of FIG. 1, in order to realize asubstantially lossless encoding-decoding step. The data expansion unit54 expands the data compressed bitstream so as to obtain a replica ofthe original bitstream, which is supplied to the input 58 of the D/Aconverter 60. The converter 60 converts the bitstream into an analogaudio signal which is supplied to the terminal 64.

FIG. 6 shows the data expansion apparatus of FIG. 5 incorporated in areproduction apparatus. The reproducing apparatus further includes aread unit 70 for reading the data compressed bitstream signal from atrack on the record carrier 32. In the present example, the recordcarrier 32 is a magnetic record carrier, so that the read unit 70includes at least one magnetic head 72 for reading the data compressedbitstream signal from the record carrier 32. The record carrier mayhowever be an optical record carrier, such as a CD disk or a DVD disk.

FIG. 7 shows an embodiment of a receiver for receiving an audio signalvia a transmission medium TRM, including the data expansion apparatus asshown in FIG. 5. The receiver further includes a receiving unit 75 forreceiving the data compressed bitstream signal from the transmissionmedium TRM. The receiving unit 75 could include an antenna 77.

As has been explained above, transmission via a transmission medium,such as a radio frequency link or a record carrier, generally requiresan error correction encoding and a channel encoding carried out on thedata compressed bitstream signal to be transmitted, so that, acorresponding channel decoding and error correction can be carried outupon reception. FIG. 9 shows the signal processing steps of channeldecoding and error correction carried out on the received signal,received by the reading apparatus 70 for the reproducing arrangement ofFIG. 6. The reproducing arrangement of FIG. 9 therefore include achannel decoder 90, well known in the art, and an error correction unit92, also well known in the art, so as to obtain a replica of the datacompressed bitstream signal.

Another data compression apparatus is shown in FIG. 10. In the datacompression apparatus of FIG. 10, the bitstream signal is supplied to aninput 8 of a lossless coder, which is in the form of an entropy coder,such as an arithmetic coder 154. Further the bitstream signal is also aninput of a prediction filter unit 152. An output of the predictionfilter unit 152 is coupled to an input of a probability determining unit156. The arithmetic coder 154 encodes the bitstream signal into a datacompressed bitstream signal in response to probability values p suppliedto its input 192. The probability determining unit 156 determines aprobability value indicating the probability that a bit in the bitstreamsignal supplied by the converter unit 4 has a predetermined logicalvalue, such as ‘1’. This probability value, denoted p in FIG. 10, issupplied to the arithmetic coder 154 so as to enable the datacompression of the bitstream signal in the arithmetic coder 154. Thedetermining unit 156 determines this probability value from the outputsignal of the prediction filter 152. The arithmetic coder 154 can datacompress the bitstream signal on a frame-by-frame basis.

The functioning of the apparatus of FIG. 10 is as follows. Theprediction filter 152 prediction filters the bitstream signal so as toobtain a multi bit output signal. The multi bit output signal has aplurality of levels within a range of eg. +3 and −3. Further, for eachof a plurality of subintervals in the value range of the multi bitoutput signal, it is determined what the probability is that thecorresponding bit in the bitstream signal is eg. a ‘1’ bit. This can berealized by counting the number of ‘ones’ and ‘zeroes’ occurring in thebitstream signal during a specific time interval, when the multi bitoutput signal falls in one of such ranges. The probabilities thusobtained for the various values in the multi bit output signal aresubsequently supplied as the probability signal p to the arithmeticcoder 154. The data compressed bitstream signal is supplied by thearithmetic coder 154 to an output line 158, for transmission via atransmission medium TRM or a record carrier.

FIG. 11 shows a corresponding data expansion apparatus for decoding thedata compressed bitstream signal, received via the transmission mediumTRM. The data processing apparatus of FIG. 11 includes an entropydecoder 172, which receives the data compressed bitstream signal via aninput 174. In the present example, the entropy decoder 172 is in theform of an arithmetic decoder that carries out an arithmetic decodingstep on the data compressed bitstream signal under the influence of aprobability signal p, supplied to an input 176 so as to generate areplica of the original bitstream signal which is supplied to an output178. The replica is supplied to an input 58 of the reconverter unit 60.

Further, a probability supply unit 180 is present for supplying theprobability signal p to the arithmetic decoder 172. The probabilitysignal p can be obtained in different ways, dependent on how theprobability signal has been derived in the encoder. One way is, toderive the probability signal p in an adaptive way from the outputsignal of a prediction filter 181. In this embodiment, the predictionfilter 181 is equivalent to the prediction filter 152 in the encoder andthe probability supply unit 180 is equivalent to the probabilitydetermining unit 156 in the encoder of FIG. 10. Another way ofgenerating the probability signal p, is by using side informationreceived via the transmission medium TRM, as will be explainedhereafter.

Side information can be generated by the apparatus of FIG. 10 fortransmission to the apparatus of FIG. 1. Such side information caninclude the filter coefficients for the filter 152 that are determinedon a frame by frame basis, which coefficients are transmitted to thecorresponding prediction filter included in the unit 180.

Further, the apparatus of FIG. 10 can generate parameters that describethe conversion of the multi bit output signal of the prediction filter152 into the probability signal p. Such parameters are also included inthe side information and transmitted to the supply unit 180 and thefilter 181, so as to enable the regeneration of the probability signal pin the apparatus of FIG. 11 on the basis of the multi bit output signalprovided by the prediction filter 181.

The entropy encoder used in the embodiment of FIG. 10 is adapted toencode the bitstream signal using a probability signal in order toobtain the data compressed bitstream signal. One such entropy encoder isthe arithmetic coder described above. One other type of such entropycoder is as an example, the well known finite state coder. The entropydecoder used in the embodiment of FIG. 11 is adapted to decode the datacompressed bitstream signal using a probability signal in order toobtain a replica of the bitstream signal. One such entropy decoder isthe arithmetic decoder described above. One other type of such entropydecoder is, as an example, the well known finite state decoder.

Whilst the invention has been described with reference to preferredembodiments thereof, it is to be understood that these are notlimitative examples. Thus, various modifications may become apparent tothose skilled in the art, without departing from the scope of theinvention, as defined by the claims. When the audio signal is suppliedin digital form, such as sampled at 44.1 kHz and the samples beingexpressed in eg. 16 bits, the conversion apparatus are adapted tooversample the digital audio signal with eg. the frequency of 64*44.1kHz so as to obtain the 1-bit bitstream signal.

It should further be noted that the invention also applies to anembodiment in which the bitstream signal, as supplied by the converter 4has undergone an additional signal processing step resulting in aprocessed 1-bit bitstream signal that is supplied to the lossless coder10. Such additional signal processing step could include merging a leftand right hand signal component of a stereo audio signal, in 1-bitbitstream form, into a processed 1-bit bitstream signal.

Further, the invention lies in each and every novel feature orcombination of features.

The invention has been disclosed with reference to specific preferredembodiments, to enable those skilled in the art to make and use theinvention, and to describe the best mode contemplated for carrying outthe invention. Those skilled in the art may modify or add to theseembodiments or provide other embodiments without departing from thespirit of the invention. The scope of the invention is not limited tothe embodiments, but lies in each and every novel feature or combinationof features described above and in every novel combination of thesefeatures. Thus, the scope of the invention is only limited by thefollowing claims:

What is claimed is:
 1. A record carrier having an audio signal recordedin a track of the record carrier, produced by the process of; receivingan input audio signal; converting the input audio signal into anuncompressed 1-bit bitstream audio signal; substantially lossless datacompressing of the uncompressed 1-bit bitstream audio signal into a datacompressed bitstream lossless audio signal; and transferring the datacompressed bitstream lossless audio signal into the track of the recordcarrier.
 2. The record carrier of claim 1, in which: wherein theconverting includes a sigma-delta modulating; the input audio signal isanalog, and the converting includes A/D converting the analog audiosignal into a 1-bit bitstream digital audio signal; the losslessencoding includes variable length encoding; the variable length encodingincludes entropy encoding; the entropy encoding is selected from aHuffman encoding and an arithmetic encoding; the process for producingthe carrier further comprises channel encoding the data compressedbitstream signal prior to applying the data compressed bitstream signalto a transmission medium; and the process for producing the carrierfurther comprises error correction encoding the data compressedbitstream signal prior to applying the data compressed bitstream signalto the transmission medium; and supplying the data compressed bitstreamlossless audio signal.
 3. The record carrier of claim 1, wherein thelossless compressing includes: entropy encoding the uncompressedbitstream audio signal in response to a probability signal, to obtainthe data compressed bitstream audio signal; predicting the uncompressedbitstream audio signal; and determining the probability signal from theprediction.
 4. The record carrier of claim 3, wherein: the predictingincludes prediction filtering of the uncompressed bitstream audio signalto obtain a multi-value output signal; and the probability determiningincludes deriving the probability signal from the multi-value outputsignal.
 5. A transmitter for transmitting a data compressed audio signalvia a transmission medium, comprising; input means for receiving aninput audio signal; means for converting of the input audio signal intoan uncompressed 1-bit bitstream audio signal; means for substantiallylossless data compressing of the uncompressed 1-bit bitstream audiosignal into a data compressed bitstream audio signal; transmission meansfor applying the data compressed bitstream audio signal to thetransmission medium; and error correction means for error correctionencoding the data compressed bitstream audio signal prior to applyingthe data compressed bitstream audio signal to the transmission medium.6. The compressor of claim 5 in which the data compressed bitstreamaudio signal is lossless.
 7. A recorder for recording an input audiosignal on a record carrier, comprising; input means for receiving theinput audio signal; conversion means for converting the input audiosignal into an uncompressed 1-bit bitstream audio signal; losslesscoding means for substantially lossless data compression of theuncompressed bitstream audio signal into a data compressed bitstreamaudio signal; writing means for writing the data compressed bitstreamaudio signal in a track on the record carrier; and error correctionencoding means for error correction encoding the data compressedbitstream audio signal prior to writing the data compressed bitstreamaudio signal on the record carrier.
 8. The compressor of claim 7 inwhich the data compressed bitstream audio signal is lossless.
 9. Areceiver for receiving an audio signal via a transmission medium,comprising: receiving means for retrieving a data compressed bitstreamaudio signal from the transmission medium; lossless decoding means forsubstantially lossless data expansion of the data compressed bitstreamaudio signal into an uncompressed 1-bit bitstream audio signal;converting means for converting the 1-bit bitstream audio signal intothe replica of the original audio signal; output means for supplying thereplica of the original audio signal, the original audio signal being amulti-bit or an analog signal; and channel decoding means for channeldecoding the data compressed bitstream audio signal retrieved from thetransmission medium prior to the lossless decoding.
 10. The compressorof claim 9 in which the data compressed bitstream audio signal islossless.
 11. Apparatus for reproducing an audio signal from a recordcarrier, comprising; means for reading a data compressed bitstream audiosignal from a track on the record carrier; lossless decoding means forsubstantially lossless data expansion of the data compressed bitstreamaudio signal into a bitstream signal; converting means for convertingthe 1-bit bitstream signal into the replica of the original audiosignal, the original audio signal being a multi-bit or an analog signal;output means for supplying the replica of the original audio signal; andchannel decoding means for channel decoding the signal read from therecord carrier, prior to the lossless decoding.
 12. The compressor ofclaim 11 in which the data compressed bitstream audio signal islossless.
 13. Apparatus for data compressing an input audio signal,comprising; input means for receiving the input audio signal; conversionmeans for converting the input audio signal into an uncompressed 1-bitbitstream audio signal; lossless coding means for substantially losslessdata compressing of the uncompressed 1-bit bitstream audio signal into adata compressed bitstream audio signal; and output means for supplyingthe data compressed bitstream audio signal; and wherein the losslesscoding means include: an entropy encoder for entropy encoding thebitstream signal in response to a probability signal, to obtain the datacompressed bitstream signal; prediction means for predicting thebitstream signal and including prediction filter means for predictionfiltering the bitstream signal to obtain a multi-value output signal;and probability signal determining means for determining the probabilitysignal from the multi-value output signal.
 14. The compressor of claim13 in which the data compressed bitstream audio signal is lossless. 15.A method for data compressing an audio signal, comprising the steps of;receiving an input audio signal; converting the input audio signal intoan uncompressed 1-bit bitstream signal; substantially lossless datacompressing of the uncompressed 1-bit bitstream audio signal into a datacompressed bitstream lossless audio signal; and supplying the datacompressed bitstream lossless audio signal; and wherein the losslesscompressing includes the substeps of; a) entropy encoding the bitstreamsignal in response to a probability signal, to obtain the datacompressed bitstream signal; b) predicting the bitstream signalincluding prediction filtering the bitstream signal, to obtain amulti-value output signal; and c) determining the probability signalfrom the multi-value output signal.
 16. The compressor of claim 15 inwhich the data compressed bitstream audio signal is lossless.
 17. Arecorder for recording an audio signal on a record carrier, comprising;input means for receiving an input audio signal; conversion means forconverting the input audio signal into an uncompressed 1-bit bitstreamaudio signal; lossless coding means for substantially lossless datacompression of the bitstream signal into a data compressed bitstreamlossless audio signal; and writing means for writing the data compressedbitstream lossless audio signal in a track on the record carrier. 18.The recorder of claim 17, wherein the record carrier is an optical or amagnetic record carrier.
 19. The recorder of claim 17, in which; theconverting means include a sigma-delta modulator; the input audio signalis analog and the converting means include A/D converting means forconverting the analog audio signal into the 1-bit bitstream digitalaudio signal; the lossless coding means include a variable lengthencoder; the variable length encoder includes an entropy encoder; theentropy encoder is selected from a Huffman encoder and an arithmeticencoder; the record carrier comprises an optical or a magnetic recordcarrier; the recorder further comprises channel encoding means forchannel encoding the data compressed bitstream signal prior to applyingthe data compressed bitstream signal to the record carrier; and therecorder further comprises error correction encoding means, for errorcorrection encoding the data compressed bitstream signal prior toapplying the data compressed bitstream signal to the record carrier. 20.The recorder of claim 17, further comprising error correction encodingmeans for error correction encoding the data compressed bitstreamlossless audio signal prior to writing the data compressed bitstreamlossless audio signal on the record carrier.
 21. The recorder of claim17, further comprising channel encoding means for channel encoding thedata compressed bitstream lossless audio signal prior to writing thedata compressed bitstream lossless audio signal on the record carrier.22. The recorder of claim 17 wherein the lossless coding means include:an entropy encoder for entropy encoding the uncompressed bitstream audiosignal in response to a probability signal, to obtain the datacompressed bitstream audio signal; prediction means for predicting theuncompressed bitstream audio signal; and probability signal determiningmeans for determining the probability signal from the bitstream audiosignal prediction.
 23. The recorder of claim 22, wherein: the predictionmeans include prediction filter means for prediction filtering theuncompressed bitstream audio signal to obtain a multi-value outputsignal; and the probability signal determining means derive theprobability signal from the multi-value output signal.
 24. Apparatus forreproducing an audio signal from a record carrier, comprising; readingmeans for reading a data compressed bitstream lossless audio signal froma track on the record carrier; lossless decoding means for substantiallylossless data expansion of the data compressed bitstream lossless audiosignal into an uncompressed 1-bit bitstream signal; converting means forconverting the uncompressed 1-bit bitstream signal into a replica of anoriginal audio signal, the original audio signal being a multi-bit or ananalog signal; and output means for supplying the replica of theoriginal audio signal.
 25. The reproducing apparatus of claim 24, inwhich; the conversion means include a sigma-delta modulator; theoriginal audio signal is analog and the converting means include D/Aconverting means for converting the 1-bit bitstream digital audio signalinto the original analog audio signal; the lossless decoding meansinclude a variable length decoder; the variable length encoder includesan entropy decoder; the entropy decoder is selected from a Huffmandecoder and an arithmetic decoder; the reproducing apparatus furthercomprises channel decoding means for channel decoding a channel encodedsignal read from the record carrier, to obtain the data compressedbitstream signal; the reproducing apparatus further comprises errorcorrection decoding means, for error correcting the signal retrievedfrom the record carrier, prior to the lossless decoding.
 26. Theapparatus of claim 24, further comprising error correction decodingmeans for error correction decoding the signal read from the recordcarrier, to obtain the data compressed bitstream lossless audio signal.27. The apparatus of claim 24, further comprising channel decoding meansfor channel decoding the signal read from the record carrier, to obtainthe data compressed bitstream lossless audio signal.
 28. The receiver ofclaim 24 wherein the lossless decoding means include: an entropy decoderfor entropy decoding the compressed bitstream audio signal in responseto a probability signal, to obtain the uncompressed bitstream audiosignal; prediction means for predicting the uncompressed bitstream audiosignal; and probability signal determining means for determining theprobability signal from the uncompressed bitstream audio signalprediction.
 29. The receiver of claim 28, wherein: the prediction meansinclude prediction filter means for prediction filtering theuncompressed bitstream audio signal to obtain a multi-value outputsignal; and the probability signal determining means derive theprobability signal from the multi-value output signal.
 30. A transmitterfor transmitting an audio signal via a transmission medium, comprising;input means for receiving an input audio signal; means for converting ofthe input audio signal into a 1-bit bitstream audio signal; means forsubstantially lossless data compressing of the uncompressed 1-bitbitstream audio signal into a data compressed bitstream audio signal;and transmission means for applying the data compressed 1-bit bitstreamsignal to the transmission medium; and channel encoding means forchannel encoding the data compressed bitstream signal prior to applyingthe data compressed bitstream signal to the transmission medium.
 31. Thecompressor of claim 30 in which the data compressed bitstream audiosignal is lossless.
 32. A recorder for recording an audio signal on arecord carrier, comprising; input means for receiving an input audiosignal; conversion means for converting the input audio signal into a1-bit bitstream audio signal; lossless coding means for substantiallylossless data compression of the bitstream signal to a data compressedbitstream signal; writing means for writing the data compressedbitstream signal in a track on the record carrier; and channel encodingmeans for channel encoding the data compressed bitstream signal prior towriting the data compressed bitstream signal on the record carrier. 33.The compressor of claim 32 in which the data compressed bitstream audiosignal is lossless.
 34. A receiver for receiving an audio signal via atransmission medium, comprising: receiving means for retrieving a datacompressed bitstream audio signal from the transmission medium; losslessdecoding means for substantially lossless data expansion of the datacompressed bitstream audio signal into an uncompressed 1-bit bitstreamsignal; converting means for converting the 1-bit bitstream signal intothe replica of the original audio signal, the original audio signalbeing a multi-bit or an analog signal; and output means for supplyingthe replica of the original audio signal; error correction means, forerror correcting the signal retrieved from the transmission medium priorto the lossless decoding.
 35. The compressor of claim 34 in which thedata compressed bitstream audio signal is lossless.
 36. Apparatus forreproducing an audio signal from a record carrier, comprising; readingmeans for reading a data compressed bitstream audio signal from a trackon the record carrier; lossless decoding means for substantiallylossless data expansion of the data compressed bitstream audio signalinto an uncompressed 1-bit bitstream signal; converting means forconverting the uncompressed 1-bit bitstream signal into a replica of anoriginal audio signal, the original audio signal being a multi-bit or ananalog signal; and output means for supplying the replica of theoriginal audio signal; error correction means, for error correcting thesignal read from the record carrier, prior to the lossless decoding. 37.The compressor of claim 36 in which the data compressed bitstream audiosignal is lossless.
 38. Apparatus for data compressing an audio signal,comprising: input means for receiving an input audio signal; conversionmeans for converting the input audio signal into an uncompressed 1-bitbitstream audio signal; lossless coding means for substantially losslessdata compressing of the uncompressed 1-bit bitstream audio signal into adata compressed bitstream audio signal; output means for supplying thedata compressed bitstream audio signal; and error correction means forerror correction encoding the data compressed bitstream audio signalprior to supplying the data compressed bitstream audio signal.
 39. Thecompressor of claim 38 in which the data compressed bitstream audiosignal is lossless.
 40. A method for data compressing an audio signal,comprising the steps of: receiving the audio signal; converting theaudio signal into an uncompressed 1-bit bitstream signal; substantiallylossless data compressing the uncompressed 1-bit bitstream audio signalinto a data compressed bitstream audio signal; supplying the datacompressed bitstream audio signal; and and error correction encoding thedata compressed bitstream audio signal prior to supplying the datacompressed bitstream audio signal.
 41. The compressor of claim 40 inwhich the data compressed bitstream audio signal is lossless.
 42. Arecord carrier having an audio signal recorded in a track of the recordcarrier, produced by the process of: receiving the audio signal;converting the audio signal into an uncompressed 1-bit bitstream audiosignal; substantially lossless data compressing the uncompressed 1-bitbitstream audio signal into a data compressed bitstream audio signal;transferring the data compressed bitstream audio signal into the trackof the record carrier; and error correction encoding the data compressedbitstream audio signal prior to transferring the data compressedbitstream audio signal into the track.
 43. The compressor of claim 42 inwhich the data compressed bitstream audio signal is lossless. 44.Apparatus for data expanding a data compressed audio signal to obtain areplica of an original audio signal, comprising: input means forreceiving a data compressed bitstream audio signal; lossless decodingmeans for substantially lossless data expansion of the data compressedbitstream audio signal into a 1-bit bitstream audio signal; means forconverting the 1-bit bitstream audio signal into the replica of theoriginal audio signal, the original audio signal being a multi-bit or ananalog signal; output means for supplying the replica of the originalaudio signal; and error correction means for error correction decodingthe data compressed bitstream audio signal prior to lossless decodingthe data compressed bitstream audio signal.
 45. The compressor of claim44 in which the data compressed bitstream audio signal is lossless. 46.A method for data expanding a data compressed audio signal to obtain areplica of an original audio signal, comprising the steps of: receivingthe data compressed audio signal as a data compressed bitstream signal;substantially lossless data expanding the data compressed bitstreamsignal into a 1-bit bitstream audio signal; converting the bitstreamsignal into the replica of the original audio signal, the original audiosignal being a multi-bit signal or an analog signal; supplying thereplica of the original audio signal; and error correction means forerror correction decoding the data compressed bitstream audio signalprior to data expanding the data compressed bitstream audio signal. 47.The compressor of claim 46 in which the data compressed bitstream audiosignal is lossless.
 48. Apparatus for data compressing an audio signal,comprising: input means for receiving an input audio signal; conversionmeans for converting the input audio signal into an uncompressed 1-bitbitstream audio signal; lossless coding means for substantially losslessdata compressing of the uncompressed 1-bit bitstream audio signal into adata compressed bitstream audio signal; output means for supplying thedata compressed bitstream audio signal; and channel encoding means forchannel encoding the data compressed bitstream audio signal prior tosupplying the data compressed bitstream audio signal.
 49. The compressorof claim 48 in which the data compressed bitstream audio signal islossless.
 50. A method for data compressing an audio signal, comprisingthe steps of: receiving the audio signal; converting the audio signalinto an uncompressed 1-bit bitstream signal; substantially lossless datacompressing the uncompressed 1-bit bitstream audio signal into a datacompressed bitstream audio signal; and supplying the data compressedbitstream audio signal; and channel encoding the data compressedbitstream audio signal prior to supplying the data compressed bitstreamaudio signal.
 51. The compressor of claim 50 in which the datacompressed bitstream audio signal is lossless.
 52. A record carrierhaving an audio signal recorded in a track of the record carrier,produced by the process of: receiving the audio signal; converting theaudio signal into an uncompressed 1-bit bitstream audio signal;substantially lossless data compressing the uncompressed 1-bit bitstreamaudio signal into a data compressed bitstream audio signal; andtransferring the data compressed bitstream audio signal into the trackof the record carrier; and channel encoding the data compressedbitstream audio signal prior to transferring the data compressedbitstream audio signal into the track.
 53. The compressor of claim 52 inwhich the data compressed bitstream audio signal is lossless. 54.Apparatus for data expanding a data compressed audio signal to obtain areplica of an original audio signal, comprising: input means forreceiving the data compressed audio signal as a data compressedbitstream signal; lossless decoding means for substantially losslessdata expansion of the data compressed bitstream audio signal into a1-bit bitstream audio signal; means for converting the 1-bit bitstreamaudio signal into the replica of the original audio signal, the originalaudio signal being a multi-bit or an analog signal; and output means forsupplying the replica of the original audio signal; and channel decodingmeans for channel decoding the data compressed bitstream audio signalprior to decoding the data compressed bitstream audio signal.
 55. Thecompressor of claim 54 in which the data compressed bitstream audiosignal is lossless.
 56. A method for data expanding a data compressedaudio signal to obtain a replica of an original audio signal, comprisingthe steps of: receiving the data compressed audio signal as a datacompressed bitstream signal; substantially lossless data expanding thedata compressed bitstream signal into a 1-bit bitstream audio signal;converting the bitstream signal into the replica of the original audiosignal, the original audio signal being a multi-bit signal or an analogsignal; and supplying the replica of the original audio signal; andchannel decoding means for channel decoding the data compressedbitstream audio signal prior to data expanding the data compressedbitstream audio signal.
 57. The compressor of claim 56 in which the datacompressed bitstream audio signal is lossless.
 58. A record carrierhaving an audio signal recorded in a track of the record carrier,produced by the process of; receiving the audio signal; converting theaudio signal into an uncompressed 1-bit bitstream audio signal;substantially lossless data compressing the uncompressed 1-bit bitstreamaudio signal into a data compressed bitstream audio signal; andtransferring the data compressed bitstream audio signal into the trackof the record carrier; supplying the replica of the original audiosignal; and wherein the lossless data compressing includes: entropyencoding the uncompressed bitstream audio signal in response to aprobability signal, to obtain the data compressed bitstream audiosignal; predicting the uncompressed bitstream audio signal by predictionfiltering the uncompressed bitstream audio signal, to obtain amulti-value output signal; and determining the probability signal fromthe multi-value output signal.
 59. The compressor of claim 58 in whichthe data compressed bitstream audio signal is lossless.
 60. A recorderfor recording an audio signal on a record carrier, comprising; inputmeans for receiving an input audio signal; conversion means forconverting the input audio signal into a 1-bit bitstream audio signal;lossless coding means for substantially lossless data compression of theuncompressed bitstream audio signal to a data compressed bitstream audiosignal; writing means for writing the data compressed bitstream audiosignal in a track on the record carrier; and wherein the lossless codingmeans include: an entropy encoder for entropy encoding the uncompressedbitstream audio signal in response to a probability signal, to obtainthe data compressed bitstream audio signal; prediction means forpredicting the uncompressed bitstream audio signal and includingprediction filter means for prediction filtering the uncompressedbitstream audio signal to obtain a multi-value output signal; andprobability signal determining means for determining the probabilitysignal from the multi-value output signal.
 61. The compressor of claim60 in which the data compressed bitstream audio signal is lossless. 62.Apparatus for reproducing an audio signal from a record carrier,comprising; reading means for reading a data compressed bitstreamlossless audio signal from a track on the record carrier; losslessdecoding means for substantially lossless data expansion of the datacompressed bitstream lossless audio signal into an uncompressed 1-bitbitstream audio signal; converting means for converting the uncompressed1-bit bitstream audio signal into a replica of an original audio signal,the original audio signal being a multi-bit or an analog signal; andoutput means for supplying the replica of the original audio signal; andwherein the lossless decoding means include: an entropy decoder forlossless data expansion of the data compressed bitstream audio signal inresponse to a probability signal, to obtain the uncompressed 1-bitbitstream audio signal; prediction means for predicting the uncompressed1-bit bitstream audio signal by prediction filtering the uncompressed1-bit bitstream audio signal to provide a multi-value output signal; andprobability signal determining means for determining the probabilitysignal from the multi-value output signal.
 63. The compressor of claim62 in which the data compressed bitstream audio signal is lossless.